@turf/standard-deviational-ellipse

@turf/standard-deviational-ellipse

standardDeviationalEllipse

Takes a FeatureCollection and returns a standard deviational ellipse, also known as a “directional distribution.” The standard deviational ellipse aims to show the direction and the distribution of a dataset by drawing an ellipse that contains about one standard deviation’s worth (~ 70%) of the data.

This module was created in consultation with the following articles:

• Robert S. Yuill, “The Standard Deviational Ellipse; An Updated Tool for Spatial Description,” Geografiska Annaler 53, no. 1 (1971): 28–39, doi:10.2307/490885.

• Paul Hanly Furfey, “A Note on Lefever’s “Standard Deviational Ellipse,” American Journal of Sociology 33, no. 1 (1927): 94—98, doi:10.1086/214336.

It mirrors the functionality of Directional Distribution in ArcGIS and the QGIS Standard Deviational Ellipse Plugin.

Parameters

• points FeatureCollection<Point> GeoJSON points
• options Object Optional parameters (optional, default {})
  • options.weight string? the property name used to weight the center
  • options.steps number number of steps for the polygon (optional, default 64)
  • options.properties Object properties to pass to the resulting ellipse (optional, default {})

Examples

var bbox = [-74, 40.72, -73.98, 40.74];
var points = turf.randomPoint(400, {bbox: bbox});
var sdEllipse = turf.standardDeviationalEllipse(points, options);

//addToMap
var addToMap = [points, sdEllipse];

Returns Feature<Polygon> an elliptical Polygon that includes approximately 1 SD of the dataset within it.

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install @turf/standard-deviational-ellipse

Or install the Turf module that includes it as a function:

$ npm install @turf/turf

Changelog

5.0.0 🎉

⭐️ Major Updates

• TurfJS now supports ES Modules (Related PR's)
• Optional parameters are now defined as an Object.

🚀 New Modules

[@turf/voronoi][voronoi]

Takes a FeatureCollection of points, and a bounding box, and returns a FeatureCollection of Voronoi polygons. (PR https://github.com/Turfjs/turf/pull/1043 - Author @stevage)

[@turf/shortest-path][shortest-path]

Returns the shortest path from start to end without colliding with any feature in obstacles (PR https://github.com/Turfjs/turf/pull/956 - Author @stebogit)

[@turf/boolean-parallel][boolean-parallel]

Boolean-Parallel returns True if each segment of line1 is parallel to the correspondent segment of line2 (PR https://github.com/Turfjs/turf/pull/941 - Author @stebogit)

[@turf/nearest-point-on-line][nearest-point-on-line]

Takes a {@link Point} and a {@link LineString} and calculates the closest Point on the (Multi)LineString. (PR https://github.com/Turfjs/turf/pull/939 - Author @stebogit)

🏅 New Features/Enhancements

• Updates [@turf/unkink-polygon][unkink-polygon] testing & added flattenEach instead of using flatten. (PR https://github.com/Turfjs/turf/pull/889)

• Add multi-geomtry support to @turf/line-split (PR https://github.com/Turfjs/turf/pull/1078)

• Improve @turf/meta lineEach method to provide properties, id and bbox (PR https://github.com/Turfjs/turf/pull/1010)

🐛 Bug Fixes

• Fixes @turf/helpers earth radius variable (PR https://github.com/Turfjs/turf/pull/1012)

• Fixes @turf/polygon-tangents bug (PR https://github.com/Turfjs/turf/pull/1058)

• Fixes @turf/line-chunk bug when the number of segments is integer (PR https://github.com/Turfjs/turf/pull/1046)

• Fixes segmentEach and segmentReduce methods in @turf/meta to ensure something is returned (PR https://github.com/Turfjs/turf/pull/968)

⚠️ Breaking Change

• Optional parameters are now defined as an Object:

Before

var from = [-75.343, 39.984];
var to = [-75.534, 39.123];
var units = 'miles';
var distance = turf.distance(from, to, units);

After

var from = [-75.343, 39.984];
var to = [-75.534, 39.123];
var options = {units: 'miles'};
var distance = turf.distance(from, to, options);

• Reworked @turf/random PR https://github.com/Turfjs/turf/issues/994
• Deprecate @turf/idw Issue https://github.com/Turfjs/turf/issues/887
• Reworked Grid modules @turf/point-grid/hex/square/triangle PR https://github.com/Turfjs/turf/pull/1029
• Renamed Modules/Methods
  • [x] @turf/inside => @turf/boolean-point-in-polygon https://github.com/Turfjs/turf/issues/860#issuecomment-317216235
  • [x] @turf/within => @turf/points-within-polygon https://github.com/Turfjs/turf/issues/860#issuecomment-317216235
  • [x] @turf/bezier => @turf/bezier-spline Issue https://github.com/Turfjs/turf/issues/661
  • [x] @turf/nearest => @turf/nearest-point https://github.com/Turfjs/turf/pull/858#issuecomment-317197295
  • [x] @turf/point-on-line => @turf/nearest-point-on-line https://github.com/Turfjs/turf/pull/858#issuecomment-317197295
  • [x] @turf/lineDistance => @turf/length https://github.com/Turfjs/turf/issues/860#issuecomment-317229869
  • [x] @turf/helpers
    • [x] radians2degrees => radiansToDegrees
    • [x] degrees2radians => degreesToRadians
    • [x] distanceToDegrees => lengthToDegrees
    • [x] distanceToRadians => lengthToRadians
    • [x] radiansToDistance => radiansToLength
    • [x] bearingToAngle => bearingToAzimuth
    • [x] convertDistance => convertLength